Middle School Physical Science : Model the law of conservation of mass using equations
Study concepts, example questions & explanations for Middle School Physical Science
All Middle School Physical Science Resources
Example Questions
Example Question #1 : Model The Law Of Conservation Of Mass Using Equations
According to the law of conservation of mass, if you start a chemical reaction with 50g of a substance, and 25g of another, you should end the reaction with: (assume this is a closed system)
less than 75 grams of whatever new substances are created because some mass will be lost in the reaction
75 grams of whatever new substances are created
25 grams of the one substance and 50 grams of the other substance
more than 75 grams of whatever new substances are created because some mass will be created in the reaction
75 grams of whatever new substances are created
The answer is "75 grams of whatever new substances are created."
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change.
Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #1 : Model The Law Of Conservation Of Mass Using Equations
In the chemical equation for Carbonic Acid, you begin with the reactants carbon dioxide and water. (CO2 + H2O) How many atoms of Oxygen would you expect to find in the symbol for carbonic acid?
3 atoms of oxygen
2 atoms of oxygen
no atoms of oxygen
1 atom of oxygen
3 atoms of oxygen
The answer is "3 atoms of Oxygen."
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change.
Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #1 : Model The Law Of Conservation Of Mass Using Equations
The image above shows the reactants in a chemical equation. How many Oxygen atoms would you expect on the other side of this equation?
4
10
2
5
10
There will be 10 Oxygen atoms in the products because there are 5 molecules of Oxygen, each with 2 bonded atoms.
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change.
Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #4 : Model The Law Of Conservation Of Mass Using Equations
The equation above shows a complete chemical reaction. How does this equation violate the law of conservation of mass?
This equation violates the law of conservation of mass because there are unequal numbers of atoms of each kind on each side.
This equation violates the law of conservation of mass because new substances are created and new atoms are formed.
This equation does not violate the law of conservation of mass because there are equal numbers of atoms of each kind on each side.
This equation does not violate the law of conservation of mass because even though the total number of atoms changes, it is an open system.
This equation does not violate the law of conservation of mass because there are equal numbers of atoms of each kind on each side.
This equation does not violate the law of conservation of mass because there are equal numbers of atoms of each kind on each side.
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change.
Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #5 : Model The Law Of Conservation Of Mass Using Equations
A student puts 26.4 grams of baking soda in a balloon and ties it over the top of the bottle containing 50 grams of vinegar. After 40 minutes passes, there is only 60 grams of liquid and baking soda at the bottom of the bottle but the balloon is blown up. What is the best explanation for this?
a chemical reaction occurred and some of the atoms were rearranged to form new substances which filled the balloon with gas
a chemical reaction did not occur so everything stays the same except atoms are always rearranging so they created a gas
a chemical reaction occurred and some of the liquid disappeared
the substance evaporated due to heat and is no longer part of the system
a chemical reaction occurred and some of the atoms were rearranged to form new substances which filled the balloon with gas
The answer is "a chemical reaction occurred and some of the atoms were rearranged to form new substances which filled the balloon with gas."
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change.
Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #6 : Model The Law Of Conservation Of Mass Using Equations
You are boiling water on a stove. The water evaporates into the air. Is this an example of a closed or an open system?
This is an example of an open system because the water vapor mixes with reactants not previously in the system.
This is an example of an open system because the water inside the pot is being introduced to the environment.
This is an example of a closed system because the water inside the pot is being introduced to the environment.
This is an example of a closed system because the water inside the pot stays in the pot.
This is an example of an open system because the water inside the pot is being introduced to the environment.
This is an example of an open system because the water inside the pot is being introduced to the environment.
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change. Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #7 : Model The Law Of Conservation Of Mass Using Equations
Is the chemical equation above an example of a closed or open system?
a closed system because mass is not conserved
an open system because mass is conserved
a closed system because mass is conserved
an open system because mass is not conserved
a closed system because mass is conserved
The answer is "a closed system because mass is conserved"
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change. Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #1 : Model The Law Of Conservation Of Mass Using Equations
What reactant is missing from the beginning of the equation below?
____ + 24F2 --> 8SF6
S8
S48
S24
S
S8
The answer is S8.
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change. Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #1 : Model The Law Of Conservation Of Mass Using Equations
What coefficient is needed in the blank before "C2H6" to balance the chemical equation below?
______C2H6 + 7O2 ---> 4CO2 + 6H2O
no coefficient is needed
3
4
2
2
The answer is "2."
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change. Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Example Question #2 : Model The Law Of Conservation Of Mass Using Equations
In the following equation, what is the missing product?
Zn + 2HCl --> ZnCl2 + ______
H2
2HCl
Cl2
Zn
H2
The answer is H2 because there are 2 Hydrogen atoms from the reactant side that are unaccounted for in the products.
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Thus, the amount of matter cannot change. Because mass is always conserved in chemical reactions, balanced chemical equations have the same number and type of each atom on both sides of the equation. Products in chemical reactions are the result of the same number of atoms being rearranged into new substances.
The law of conservation of mass only applies in “closed systems” meaning that the mass and energy is not able to escape to the environment. For example, if you are boiling water on the stove and you put a lid on your pot, the water vapor will collect inside the pot. This is a closed system, and the amount of mass will not change, though it will be converted from liquid to gas. If you take the lid off your pot, the evaporated water will escape into your kitchen and the total amount of matter will change. You opened your system!
Certified Tutor
Certified Tutor
All Middle School Physical Science Resources
